Organic electroluminescence device and manufacturing method therefor

ABSTRACT

An organic EL device in accordance with the invention has a structure in which a first electrode, a light-emitting layer, and a second electrode are formed on a substrate in this order, and light from the light-emitting layer is emitted to an exterior of the device via the second electrode.

This is a Division of application Ser. No. 09/790,546 filed Feb. 23,2001. The entire disclosure of the prior application is herebyincorporated by reference herein in its entirety.

The present invention relates to the structure of an electroluminescent(in this specification, referred to as organic EL) device for use as adisplay device in an information terminal apparatus, such as a computer,a mobile phone, or a television, and also relates to a manufacturingmethod thereof.

Recently, there has been an increasing trend toward portability ofinformation terminals, and development of power saving displays, whichare necessary to enhance portability. Among displays, organic ELdisplays in particular have drawn attention, and the development thereofis at the stage of pursuing practical applications.

In order to realize power saving displays, it is believed that it ismost effective to drive an organic EL element by an active element, suchas a thin-film transistor (TFT). The reason for this is that, when anactive element is used, an organic EL element can be driven by a DCvoltage, and can be driven at a low voltage without imposing a loadthereon in the range of high luminous efficiency. In the case of simplematrix driving, which uses no active devices, the luminance must beincreased by applying a high voltage during a selection period.Accordingly, a significant load is imposed on the organic EL element,and in addition, the luminance efficiency is decreased. As a result, thelife thereof is naturally shortened.

An active matrix method using a TFT or the like is a strong candidatefor use in a power saving organic EL display; however, it has theshortcoming that the aperture ratio, which indicates the ratio of thelight-emitting area to the display area for display, is decreased. Whenthe aperture ratio is decreased, luminance in each pixel must beenhanced in order to increase the display luminance. In the casedescribed above, a driving voltage is increased, power consumption isthereby increased, and hence, a problem may arise in that the life isshortened due to the load imposed on the organic EL element. In order tosolve the problem described above, as shown in FIG. 2, in the structureof an organic EL element (device), a transparent cathode can be formedin order to emit light from a side opposite to the substrate (IEEE,TRANSACTIONS ON ELECTRON DEVICES, VOL. 44, NO. 8, PP 1188-1203). Inparticular, an anode 5, a hole injection layer 4, a light-emitting layer3, a cathode 2, and a transparent auxiliary cathode 21 are sequentiallyformed on a substrate 1 in this order, and light is emitted from thetransparent auxiliary cathode 21 side. In the structure described above,the light may not be emitted from the TFT substrate side; however, thelight transmittance of the cathode used in the structure described aboveis approximately one-half of that of the substrate, and as a result, aproblem may arise in that the brightness of the display is actuallyreduced.

The invention solves the problems described above, and an object of thepresent invention is to provide an arrangement of elements in which theaperture ratio and the light transmittance are not degraded even when aswitching element is used. It is also an object of the invention toprovide a manufacturing method thereof. In other words, an organic ELdevice is provided which consumes low electric power and has a longlife. In addition, a structure is also proposed in which a decrease incontrast is prevented, which is caused by incident outside light,without decreasing the luminance.

According to the present invention, an organic EL device is providedincluding at least a cathode, a light-emitting layer, and an anodeformed on a substrate in this order.

In addition, according to the present invention, an organic EL deviceincludes a plurality of pixels provided on a substrate, in which each ofthe plurality of pixels is in an area defined by a partition, a firstelectrode, a light-emitting layer, and a second electrode are formed inthe area in this order, and light from the light-emitting layer isemitted outside from the second electrode side.

In addition, according to the present invention, a method formanufacturing an organic EL device is provided in which at least acathode, a light-emitting layer, and a transparent anode are formed on asubstrate in this order.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing the structure of an organic ELdevice according to Embodiment 1.

FIG. 2 is a cross-sectional view showing the structure of a related artorganic EL device for comparison to Embodiment 1 of FIG. 1.

FIG. 3 is a cross-sectional view showing the structure of an organic ELdevice according to Embodiment 3.

FIG. 4 is a cross-sectional view showing the structure of an organic ELdevice according to Embodiment 4.

FIG. 5 is a cross-sectional view showing the structure of an organic ELdevice according to Embodiment 7.

FIG. 6 is a cross-sectional view showing the structure of an organic ELdevice relating to Embodiment 7.

FIG. 7 is a schematic view showing a plan structure of an organic ELdevice (display device) according to Embodiment 8.

FIG. 8 is a cross-sectional view showing the structure of an organic ELdevice according to Embodiment 9.

FIG. 9 is a cross-sectional view showing the structure of an organic ELdevice according to Embodiment 11.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first characteristic of the present invention is that in an organic ELdevice, at least a cathode, a light-emitting layer, and an anode areformed on a substrate in this order.

According to the arrangement described above, since light can be emittedto a side opposite to the substrate when observed from thelight-emitting layer, an opaque material can be used at the substrateside. For example, a semiconductor substrate, such as silicon, or ametal substrate, may be used. Accordingly, an integrated circuit isformed on a silicon substrate, and an organic EL element (device) can beformed thereon. In addition, a hole transport layer and/or a holeinjection layer are preferably formed between the light-emitting layerand a transparent anode.

As an example of the embodiment, for example, the following modes may bementioned.

(1) In the organic EL device having the first characteristic arrangementdescribed above, the cathode includes a laminate of at least one type ofconductive material and a metal oxide or fluoride.

According to this arrangement, in the organic EL device, the luminousefficiency can be further enhanced.

(2) In the organic EL device having the first characteristic arrangementdescribed above, a plurality of pixels is provided, cathodescorresponding to the plurality of pixels are formed on the substrate,pixel partitions formed of an insulating material are formed between thepixels, and auxiliary anodes including a conductive material are formedhaving patterns equivalent to those of the partitions at locationscorresponding to the top surfaces of the partitions formed of theinsulating material.

According to this arrangement, the resistance of the transparent anodehaving a relatively high resistance can be decreased by using theauxiliary anode, and as a result, an organic EL device uniformlyemitting light from the entire surface thereof can be realized.

(3) In the organic EL device having the first characteristic arrangementdescribed above, a plurality of pixels is provided, cathodescorresponding to individual pixels are formed on the substrate, pixelpartitions formed of an insulating material are formed between thepixels, and at least the cathode, the light-emitting layer, the anode,and an auxiliary anode are formed in each pixel in this order.

According to this arrangement, the auxiliary anode can be formed in asubsequent step, various materials can be used for the auxiliary anodeas the effect, and advantages can be obtained relating to particularfeatures of the material. A mask deposition method, an inkjet method, aprinting method, or the like may be used for patterning the auxiliaryanode.

(4) In the organic EL device as described in headings (2) or (3), theauxiliary anode includes a light-absorbing conductive material.

According to this arrangement, when the display is observed from a sideto which light is emitted, since the light-absorbing auxiliary anodesare seen between the pixels, outside light is absorbed, and the contrastcan be enhanced, whereby the display becomes easy to see.

(5) In the organic EL device as described in heading (4), the auxiliaryanode includes carbon or chromium.

According to this arrangement, outside light is more effectivelyabsorbed between the pixels.

(6) In the organic EL device having the first characteristic arrangementdescribed above, an active matrix structure containing switchingelements is provided on the substrate, and a laminate structure of atleast the cathode, the light-emitting layer, and the anode are formed soas to overlap at least a part of the switching element when viewed fromthe top side.

According to this arrangement, an area of an aperture portion in thepixel can be designed independently from a circuit relating to theswitching element, which significantly increases the aperture ratio.

(7) In the organic EL device having the first characteristic describedabove, a semiconductor substrate having an integrated circuit thereon isused as the substrate.

According to this arrangement, all electronic circuits required for thedevice, such as electronic circuits for a portable terminal,controllers, drivers, and power circuits used for display driving, canbe formed on the semiconductor substrate formed of the siliconsubstrate, and in addition, transistors and the like that drive theorganic EL device can also be provided thereon, whereby higherperformance of the device and cost reduction thereof can besimultaneously realized.

(8) In the organic EL device as described in headings (3) or (4), afterthe anodes and/or the auxiliary anodes are formed, a protectivesubstrate having a light-absorbing layer formed at positionscorresponding to areas between the pixels is disposed so that the pixelsand areas of the protective substrate corresponding thereto are alignedwith each other, and the protective substrate is then bonded to thepixels with a sealing resin provided therebetween.

According to this arrangement, since light-absorbing portions can beprovided between the pixels in addition to the auxiliary anodes, theauxiliary anodes and the light-absorbing material can be optimized.

(9) A method for manufacturing an organic EL device includes forming atleast a cathode, a light-emitting layer, and an anode on a substrate inthis order.

According to this method, it is preferable that a hole transport layerand/or a hole injection layer be formed on the light-emitting layer, andthe anodes can be subsequently formed.

(10) The method for manufacturing an organic EL device as described inheading (9) further includes performing a treatment for impartinghydrophilic properties to the surface of the light-emitting layer.

According to this method, a water-soluble solution containing a holeinjection material can be uniformly coated. As a common method therefor,an oxygen plasma irradiation method is used.

(11) A method for manufacturing an organic EL device includes the stepsof forming at least insulating pixel partitions on a substrate,subsequently depositing a light-reflecting cathode material on theentire surface and simultaneously forming cathodes and auxiliaryelectrodes by separating the cathodes and the auxiliary anodes on thepartitions using steps thereof, and subsequently forming at least alight-emitting layer, and anodes in the areas defined by the partitionsin this order.

According to this method, patterning for the auxiliary anodes is notnecessary, and the cost can be reduced.

(12) A method for manufacturing an organic EL device includes the stepsof, after the cathodes are formed on the substrate, coating the entiresurface of the substrate with an insulating material for pixelpartitions followed by calcining, forming a film formed of a materialfor auxiliary anodes over the entire surface, subsequently etching thefilm of the material for the auxiliary anodes for patterning in aphotolithographic step, subsequently etching the pixel partition layerthereunder for patterning, firing the partition layer, and subsequentlyforming at least a light-emitting layer and an anode in this order ineach area defined by the partition.

According to this method, patterning for the pixel partitions and theauxiliary anodes can be simultaneously performed.

Hereinafter, particular embodiments of the present invention will bedescribed.

Embodiment 1

In this embodiment, an example will be described in which at least acathode, a light-emitting layer, a transparent anode, and a holetransport layer and/or a hole injection layer are formed on a substratein this order. In FIG. 1, a cross-sectional view of an organic EL deviceaccording to this embodiment is shown.

First, a cathode 2 was formed on a substrate 1. Next, a light-emittinglayer 3 was formed, and in addition, a hole injection layer 4 wasformed. Next, an anode 5 was formed, and in addition, a sealing layer(not shown in the figure) was formed.

When a voltage was applied between electrodes of the organic EL devicethus formed, light was emitted from the sealing layer side.

For the substrate 1 used in this embodiment, in addition to a glasssubstrate, a metal, a semiconductor, a plastic, or the like may be used,and an opaque substrate may also be used.

For the cathode 2 used in this embodiment, aluminum, magnesium, lithium,or calcium may be used, and in addition, the alloy thereof or a laminateformed of these metals (in this case, a layer having a smaller workfunction is disposed at the light-emitting layer side) may also be used.

For the light-emitting layer 3 used in this embodiment, a polymericmaterial, or a low molecular weight material may be used. For example,PPV, polydioctylfluorene, polyfluorene, Alq3, DPVBi, and the like may beused.

For the hole injection layer/hole transport layer 4, in addition toBytron manufactured by Bayer AG., a common material, such as lowmolecular material TPD, MTDATA, or copper phthalocyanine, may also beused.

For the anode 5 used in this embodiment, in addition to ITO, a Nesafilm, IDIXO sold by Idemitsu Kosan Co., Ltd., or the like may also beused. In particular, IDIXO is preferably used since satisfactoryconductive characteristics can be obtained even when the film thereof isformed at room temperature.

For sealing, a thermosetting epoxy resin was used; however, anultraviolet curable resin may also be used. In addition, it is effectiveto use a protective substrate together therewith.

According to the arrangement of this example, since light can be emittedfrom a side opposite to the substrate when observed from thelight-emitting layer, an opaque material can be used at the substrateside. For example, a semiconductor substrate, such as silicon, or ametal substrate may be used. As a result, an integrated circuit isformed on a silicon substrate, and an organic EL element (device) can beformed thereon.

Embodiment 2

In this embodiment, a particular example will be described in which thecathode is formed of a laminate formed of at least one type ofconductive material and a metal oxide or fluoride. By using the methodof Embodiment 1, when patterning was performed in a photolithographicstep after an aluminum film was formed as a cathode, and an oxygenplasma treatment was then performed, an oxide layer 20 Å thick wasformed on the surface. By using this substrate provided with thecathode, when an organic EL device was formed by performing theoutstanding steps in Embodiment 1, the luminous efficiency thereof wastwo times (0.2 lm/W) that obtained in Embodiment 1.

Instead of the oxygen plasma treatment performed on the surface of thecathode, when lithium fluoride 20 Å thick was deposited, the luminousefficiency was 0.5 lm/W.

The light-emitting layer 3 used in this embodiment was formed of apolyfluorene material and was formed by spin coating. The hole injectionlayer 4 was formed by spin coating using Bytron manufactured by BayerAG. The anode 5 was formed of IDIXO. Materials and conditions for filmformation are not limited to those described above.

Embodiment 3

In this embodiment, an example of the structure shown in FIG. 3 will bedescribed in which a plurality of cathodes 2 corresponding to aplurality of light-emitting pixels are formed on a substrate 1, pixelpartitions 6 formed of an insulating material are formed between thelight-emitting pixels, and auxiliary anodes 7 formed of a conductivematerial having approximately equivalent patterns to those of the pixelpartitions 6 are formed thereon.

A particular example is described below. First, after the cathodes 2were patterned, the pixel partitions 6 were formed of a polyimide andwere patterned, and subsequently, a film formed of tantalum 1,000 Åthick was formed and was then patterned so as to form the same patternas that of the pixel partition 6. Next, a film formed of lithiumfluoride 20 Å thick was formed on the entire surface, three types ofpolyfluorene materials emitting red, green, and blue light were eachdissolved in isodurene, and the films thereof as the light-emittinglayers 3 were formed in red, green, and blue pixels, respectively, bypatterning using an inkjet method. Next, films formed of Bytronmanufactured by Bayer AG. were formed by patterning in the individualpixels using an inkjet method as the hole injection layer 4. Next, asthe anodes 5, a film of IDIXO manufactured by Idemitsu Kosan Co., Ltd.was formed by sputtering. In addition, sealing was performed by using anepoxy sealing material 8 and a protective substrate 9. To the individualpixels of the organic EL device thus formed, when voltages for red,blue, and green were independently applied, a uniform color image couldbe observed in accordance with the applied voltages.

In addition, as a reference, when an element provided with no auxiliaryanode 7 was formed, pixels in the vicinity of lead wires for the anodesonly emit light.

For the cathode, the light-emitting material, the material for the holeinjection material, the anode, the auxiliary anode, and the sealingmaterial used in this embodiment, the materials used in Embodiment 1 mayalso be used. In addition, as a film formation method, an inkjet method,a mask deposition method, a printing method, or the like may also beused.

In a structure similar to that in this embodiment, an arrangement can beformed in which an opaque layer formed of Pt, Ir, Ni, Pd, Au, a laminateof ITO and Al, or the like is formed as a layer located at the positionof the cathode 2; and a layer having a predetermined thickness formed ofgold, calcium, aluminum, a laminate thereof, a layer formed byco-deposition of Mg and silver, or the like is formed as a transparentlayer at the position of the anode 5. In this arrangement, by drivingthe layer located at the position of the cathode 2 and the layer locatedat the position of the anode 5 as an anode and a cathode, respectively,the light can be emitted from the light-emitting layer toward the upperlayer via the protective substrate. In the case described above, theauxiliary anode 7 is used as an auxiliary layer for the cathode.

Embodiment 4

In this embodiment, an example will be described in which a plurality ofcathodes 2 corresponding to a plurality of light-emitting pixels areformed on the substrate, pixel partitions formed of an insulatingmaterial are formed between the light-emitting pixels, and in eachpixel, at least a cathode, a light-emitting layer, a transparent anode,and an auxiliary anode 7 are formed in this order.

In FIG. 4, a cross-sectional structure of an organic EL device of thisembodiment is shown.

After cathodes 2 were patterned, pixel partitions 6 were formed of apolyimide and were patterned. Next, a film formed of calcium fluoride 20Å thick was formed over the entire surface, films of three types of lowmolecular materials emitting red, green, and blue light were formed inred, green, and blue pixels, respectively, by patterning using a maskdeposition method. Next, as a hole injection layer 4, TPD and MTDATAwere sequentially deposited over the entire surface. Next, as anodes 5,IDIXO manufactured by Idemitsu Kosan Co., Ltd. was sputtered.Subsequently, tantalum 1,000 Å thick was formed by mask deposition andwas then patterned. In addition, sealing was performed by an epoxysealing material 8 and a protective substrate 9. To the individualpixels of the organic EL device thus formed, when voltages for red,blue, and green were independently applied, a uniform color image can beobserved in accordance with the applied voltages.

As a reference example, when an element that was not provided with anauxiliary anode 7 was formed, only pixels in the vicinity of lead wiresfor the anodes emit light.

For the cathode, the light-emitting material, the hole injectionmaterial, the anode, the auxiliary anode, and the sealing material usedin this embodiment, the materials used in Embodiment 1 may also be used.In addition, as a film formation method, an inkjet method, a printingmethod, or the like may also be used besides a mask deposition method.

In addition, as is the case described in Embodiment 3, when a layer atthe position of the cathode 2 and a layer at the position of the anode 5are formed of particular materials having particular thicknesses or thelike, respectively, the layer at the position of the cathode 2 and thelayer at the position of the anode 5 can also be driven as an anode anda cathode, respectively, so that the light is emitted from thelight-emitting layer toward the outside via the protective substrate.

Embodiment 5

In this embodiment, an example will be described in which the auxiliaryanode described above is formed of a light-absorbing conductivematerial.

Chromium was used instead of tantalum used for the auxiliary anode 7 inEmbodiment 3. As a result, since the reflectance of chromium was 60%,the reflectance of outside light was decreased, and hence, enhancementin contrast could be observed.

As the light-absorbing conductive material, in addition to the chromiumdescribed above, a polymeric conductive material, such as Bytronmanufactured by Bayer AG., or polyaniline, or carbon may also be used.

Embodiment 6

In this embodiment, an example will be described in which the auxiliaryanode described above is formed of a light-absorbing conductivematerial, and in particular, the auxiliary anode is formed of carbon.

Carbon was used instead of tantalum used for the auxiliary anode 7 inEmbodiment 4. The film formation thereof was performed by a maskdeposition method. As a result, the reflectance of outside light wasdecreased to nearly zero, and the contrast could be significantlyincreased.

As the light-absorbing conductive material, in addition to carbon, apolymeric conductive material, such as Bytron manufactured by Bayer AG.,or polyaniline, or chromium may also be used.

Embodiment 7

In this embodiment, an example will be described in which an activematrix structure having switching elements is laminated on a substrate,and a pixel laminate structure formed of a cathode, a light-emittinglayer, and an anode, is formed so as to overlap at least a part of theactive matrix structure, in particular, at least a part of the switchingelement when viewed from the top side. In FIG. 5, a cross-sectionalstructure of an organic EL device of this embodiment is shown.

The structure in the figure is formed of the structure shown in FIG. 3as a base material and a thin-film transistor (hereinafter referred toas “TFT”) provided on the substrate as a switching element.

An aperture delimiter 11 is provided in a layer under a pixel partition,which defines a light-emitting area for the light from thelight-emitting layer. In addition, as another example, a cross-sectionalstructure of an organic EL device is shown in FIG. 6 in which an anode,a cathode, and an anode are sequentially formed on a substrate in thisorder, and an area at which a TFT element 10 as a switching element isdisposed is located under a pixel partition so as to substantiallyoverlap the partition when viewed from the top side.

As shown in FIG. 5, above the substrate provided with the TFT element10, a light-emitting pixel structure (a laminate structure formed of acathode 2, a light-emitting layer 3, and an anode 5) having anarrangement (additionally provided with an aperture delimiter 11)similar to that shown in FIG. 3 was formed. Similarly to the above, anorganic EL device having a light-emitting pixel structure, which isshown in FIG. 6, was formed.

The organic EL device having the structure shown in FIG. 5 was driven sothat the light was emitted to the anode 5 side, and the organic ELdevice having the structure shown in FIG. 6 was driven so that the lightwas emitted to the substrate 1 side. Compared to the structure (theaperture ratio was 30%) shown in FIG. 6, in the structure shown in FIG.5, by virtue of the pixel structure provided at a side (substrate side)opposite to the side which the light is emitted to, in particular, byvirtue of the switching element provided so as to overlap thelight-emitting layer when viewed from the top side, the aperture ratio,which could make the light-emitting layer work, could be enhanced (theaperture ratio was 70%). Conventionally, in order to obtain a displayluminance of 100 Cd/m2, a driving voltage of 6 volts is required;however, in this embodiment, 5 volts becomes enough to obtain a displayluminance of 100 Cd/m2. Accordingly, the life is increased to 10 timesthat of the conventional structure.

According to this embodiment, an area of the pixel aperture can bedesigned independently from the switching element, such as a TFTcircuit, and hence, the aperture ratio can be significantly improved.

In the structure shown in FIG. 5, as is the case described in Embodiment3, when a layer at the position of the cathode 2 and a layer at theposition of the anode 5 are formed of particular materials havingparticular thicknesses or the like, respectively, the layer at theposition of the cathode 2 and the layer at the position of the anode 5can also be driven as an anode and a cathode, respectively, so that thelight is emitted from the light-emitting layer toward the outside viathe protective substrate.

In addition, in the structure shown in FIG. 6, as is the case describedin Embodiment 3, when a layer at the position of the cathode 2 and alayer at the position of the anode 5 are formed of particular materialshaving particular thicknesses or the like, respectively, the layer atthe position of the cathode 2 and the layer at the position of the anode5 can also be driven as an anode and a cathode, respectively, so thatthe light is emitted from the light-emitting layer toward the outsidevia the protective substrate. In the case described above, the apertureratio can be enhanced similar to the structure shown in FIG. 5.

Embodiment 8

In embodiment, a semiconductor substrate having an integrated circuitformed thereon is used as a substrate to be used. In this embodiment, anexample will be described in which an electronic circuit for a mobilephone, a controller and a driver for display driving, and also atransistor for driving an organic EL device are formed on a siliconsubstrate, and the organic EL device is formed at a display portion. InFIG. 7, a schematic view of the silicon substrate provided with theorganic EL device of this embodiment formed thereon is shown.

As shown in the figure, an organic EL device display portion 12 isprovided on a silicon substrate 18 in which organic EL elements (a pixelstructure) as shown in the embodiment described above are disposed in anXY matrix, an X driver 14 and a Y driver 13 for use in a matrix drivingof the display portion are provided in the vicinity thereof, and inaddition, a controller 15, an electronic circuit 16, and a power supplycircuit 17 are provided and are connected to the power supply andswitches. According to the arrangement described above, operations, suchas those of a mobile phone, can be realized by forming every circuit ona one piece silicon substrate and by using switches to control from theexterior of the structure.

In this embodiment, the mobile phone is described by way of example, andin addition, this embodiment can also be used for applications whichrequire power saving, and reduction in weight.

Embodiment 9

In this embodiment, an example will be described in which after theanode or the auxiliary anode is formed, a protective substrate having alight-absorbing layer formed at a position corresponding to eachposition between the pixels is bonded to the pixels with a sealingmaterial provided therebetween while the pixels on the substrate andareas of the protective substrate corresponding to pixels are alignedwith each other. In FIG. 8, a cross-sectional structure of an organic ELdevice of this embodiment is shown.

A sealing material 8 is coated on the substrate provided with the anodedescribed in Embodiment 3, and a light-absorbing layer 19 is formed soas to correspond to areas between the pixels. A protective substrate 9is bonded thereto for fixing while being aligned. The organic EL devicethus formed performs sufficiently uniform display by virtue of theeffect of the auxiliary anode and can efficiently damp the reflection ofoutside light, whereby display can be performed having a superiorcontrast.

Embodiment 10

In this embodiment, an example will be described in which after thelight-emitting layer is formed, a treatment for imparting hydrophilicproperties is performed to the surface of the light-emitting layer in amethod for manufacturing an organic EL device having at least a cathode,a light-emitting layer, a hole transport layer and/or a hole injectionlayer, and a transparent anode formed on a substrate in this order, andmore particularly, in a method for manufacturing an element having thestructure shown in FIG. 1.

In FIG. 1, when a polyfluorene material is used for a light-emittinglayer 3, film formation of Bytron manufactured by Bayer AG., which iscommonly used for a hole injection layer 4, may not be sufficientlyperformed in some cases due to the poor wettability thereof.Accordingly, after the light-emitting layer 3 was formed, when Bytronwas spin-coated while oxygen plasma irradiation is performed, a uniformfilm could be obtained. The organic EL device thus formed emits lightuniformly over the entire surface.

In this embodiment, as a method for imparting hydrophilic properties tothe surface of the light-emitting layer, a UV ozone treatment may alsobe used.

As the material for the hole injection layer in this embodiment, asolution having a high polarity, such as a solution containing apolyaniline salt, may be used.

Embodiment 11

In this embodiment, an example will be described in which at leastinsulating pixel partitions are formed on a substrate, a film for areflective cathode is then formed over the entire surface andsimultaneously cathodes and auxiliary anodes on the partition areseparated from each other by steps thereof, and subsequently at least alight-emitting layer and a transparent anode are formed in the pixel inthis order. In FIG. 9, a cross-sectional structure of an organic ELdevice of this embodiment is shown.

After a lead wire 20 for the cathode was patterned, and a pixelpartition 6 was formed, aluminum was deposited as a cathode 2. In thestep described above, a cathode pattern was formed by the wall of thepixel partition 6, and a pattern of an auxiliary anode 7 wassimultaneously formed.

When an angle of the wall of the pixel partition 6 is determined so asto incline toward the exterior of the structure, patterning can bereliably performed; however, since wire breakage may occur until ananode 5 is subsequently formed, optimization is required.

Embodiment 12

In this embodiment, an example will be described in which, aftercathodes are formed on a substrate, and an insulating material for pixelpartitions is then coated on the entire surface and is calcined, a filmformed of a material for an auxiliary anode is formed over the entiresurface, the auxiliary anode layer is first etched for patterning in aphotolithographic step, the pixel partition layer thereunder is thenetched for patterning, the pixel partition layer is fired, andsubsequently, at least a light-emitting layer and a transparent anodeare formed in the pixel in this order. In particular, an element havingthe structure shown in FIG. 3 is formed.

First, a cathode 2 having a pattern was formed on a substrate 1. Next, apolyimide solution as a material for an insulating pixel partition 6 wascoated over the entire surface of the substrate and was then calcined.Subsequently, tantalum having a film thickness of 1000 Å, which was tobe used as an auxiliary anode 7, was formed by sputtering. Next, aresist was coated thereon and was then exposed. After development, thetantalum was etched. Subsequently, the polyimide was etched. Next, theresist was stripped away, and the polyimide was fired, whereby astructure having the pixel partitions 6 and the auxiliary anodes 7 wascompleted.

As the material for the pixel partition or the material for theauxiliary electrode, a material which can be patterned by a photographicstep may also be used.

As has thus been described in detail, according to the presentinvention, when the structure is formed in which the cathode, thelight-emitting layer, and the anode are formed in this order on thesubstrate of the organic EL device, an element arrangement can beprovided in which the aperture ratio and the light transmittance are notdecreased even when active elements are used, and in addition, amanufacturing method therefor can be provided. Accordingly, an organicEL device can be provided which consumes low electric power and also hasa long life. In addition, at the same time, an organic EL device can berealized having a structure which prevents a decrease in contrast due toincident outside light without decreasing the luminance.

1. An organic EL device comprising: a substrate; a plurality of pixels,a plurality of first electrodes corresponding to the plurality of pixelsbeing formed on the substrate, a light-emitting layer formed over thefirst electrodes; a pixel partition including an insulating materialbeing formed between the pixels, an auxiliary electrode including aconductive material and having a pattern equivalent to that of thepartition being formed at a position corresponding to a top surface ofthe partition that includes the insulating material; and a secondelectrode continuous over the light-emitting layer and the auxiliaryelectrode.
 2. The organic EL device according to claim 1, the pixelpartition including a first layer and second layer.
 3. The organic ELdevice according to claim 2, the first layer protruding from the secondlayer and delineating the light-emitting layer.
 4. An organic EL devicecomprising: a substrate; a plurality of pixels, a plurality of firstelectrodes corresponding to the plurality of pixels being formed on thesubstrate, a pixel partition including an insulating material beingformed between the pixels, a light-emitting layer formed over the firstelectrodes; a second electrode continuous over the light-emitting layerand the pixel partition; a auxiliary electrode including a conductivematerial being formed over the second electrode at a positioncorresponding to the pixel partition.
 5. The organic EL device accordingto claim 4, the substrate being a semiconductor substrate having anintegrated circuit formed thereon.
 6. The organ EL device according toclaim 5, the integrated circuit including at least one of a controller,a power supply circuit, an X driver and a Y driver.
 7. The organic ELdevice according to claim 4, wherein, after at least one of the secondelectrode and the auxiliary electrode are formed, a protective substratehaving a light-absorbing layer formed at a position corresponding to aposition between the pixels is disposed so that the pixel and an area ofthe protective substrate corresponding to the pixel are aligned witheach other, and the protective substrate is subsequently bonded theretowith a sealing resin provided therebetween.
 8. The organic EL deviceaccording to claim 4, the pixel partition including a first layer and asecond layer.
 9. The organic EL device according to claim 8, the firstlayer protruding from the second layer and delineating thelight-emitting layer.
 10. The organic EL device according to claim 4,the auxiliary electrode including a light-absorbing conductive material.11. The organic EL device according to claim 10, the auxiliary electrodeincluding carbon or chromium.